Slow turning gear adapter to eliminate turbine bucket wear

Abstract

A turbine and the method of operating the turbine when taking the turbine off-line includes transmitting power to a No. 1 shaft via a main motor to turn the turbine at an original turning speed, wherein the No. 1 shaft drives a No. 2 shaft; reducing a speed of the turbine; and when the speed of the turbine is reduced to a predetermined RPM, switching power transmission to the turbine from the No. 1 shaft to a No. 2 shaft, wherein the No. 2 shaft is driven by an auxiliary motor, and the No. 2 shaft drives the No. 1 shaft to turn the turbine at a slow turning speed less than the original turning speed.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. A method of operating a turbine when taking the turbine off-line, comprising:
 transmitting power to a No. 1 shaft via a main motor to turn the turbine at an original turning speed, wherein the No. 1 shaft drives a No. 2 shaft; 
 reducing a speed of the turbine; and 
 when the speed of the turbine is reduced to a predetermined RPM, and upon reaching a predetermined time of running the turbine at the original turning speed, switching power transmission to the turbine from the No. 1 shaft to the No. 2 shaft, wherein the No. 2 shaft is driven by an auxiliary motor, and the No. 2 shaft drives the No. 1 shaft to turn the turbine at a slow turning speed less than the original turning speed, wherein the turbine comprises turbine buckets attached by bucket roots on a turbine wheel. 
 
     
     
       2. The method of  claim 1 , wherein the original turning speed is greater than 40 RPM, and the slow turning gear speed is less than 10 RPM. 
     
     
       3. The method of  claim 1 , wherein the original turning speed is used during cool down of a turbine shaft, and the slow turning speed is used after the turbine shaft has cooled down. 
     
     
       4. The method of  claim 1 , further comprising engaging a clutch to transmit power from the auxiliary motor to the No. 2 shaft. 
     
     
       5. The method of  claim 4 , further comprising turning off the main motor to reduce the turbine speed before the clutch is engaged. 
     
     
       6. The method of  claim 1 , further comprising, after the turbine has been running at the slow turning speed, increasing the speed of the turbine, and when the speed of the turbine is increased to a predetermined RPM, switching power transmission to the turbine from the No. 2 shaft to the No. 1 shaft. 
     
     
       7. The method of  claim 6 , further comprising disengaging a clutch upon reaching the predetermined RPM. 
     
     
       8. The method of  claim 6 , further comprising turning on the main motor to increase the speed of the turbine. 
     
     
       9. The method of  claim 1 , wherein the No. 1 shaft and the No. 2 shaft are located within an accessory gear box. 
     
     
       10. The method of  claim 1 , wherein the No. 1 shaft comprises a set of helical gears and the No. 2 shaft comprises a set of helical gears, wherein the helical gears of the No. 1 shaft are intermeshed with the helical gears of the No. 2 shaft. 
     
     
       11. A method of operating a turbine when taking the turbine off-line, comprising:
 transmitting power to a No. 1 shaft via a main motor to turn the turbine at an original turning speed, wherein the No. 1 shaft drives a No. 2 shaft; 
 reducing a speed of the turbine; and 
 when the speed of the turbine is reduced to a predetermined RPM, and upon reaching a predetermined turbine temperature while running the turbine at the original turning speed, switching power transmission to the turbine from the No. 1 shaft to the No. 2 shaft, wherein the No. 2 shaft is driven by an auxiliary motor, and the No. 2 shaft drives the No. 1 shaft to turn the turbine at a slow turning speed less than the original turning speed, wherein the turbine comprises turbine buckets attached by bucket roots on a turbine wheel. 
 
     
     
       12. The method of  claim 11 , wherein the original turning speed is greater than 40 RPM, and the slow turning gear speed is less than 10 RPM. 
     
     
       13. The method of  claim 11 , wherein the original turning speed is used during cool down of a turbine shaft, and the slow turning speed is used after the turbine shaft has cooled down. 
     
     
       14. The method of  claim 11 , further comprising engaging a clutch to transmit power from the auxiliary motor to the No. 2 shaft. 
     
     
       15. The method of  claim 14 , further comprising turning off the main motor to reduce the turbine speed before the clutch is engaged. 
     
     
       16. The method of  claim 11 , further comprising, after the turbine has been running at the slow turning speed, increasing the speed of the turbine, and when the speed of the turbine is increased to a predetermined RPM, switching power transmission to the turbine from the No. 2 shaft to the No. 1 shaft. 
     
     
       17. The method of  claim 16 , further comprising disengaging a clutch upon reaching the predetermined RPM. 
     
     
       18. The method of  claim 16 , further comprising turning on the main motor to increase the speed of the turbine. 
     
     
       19. The method of  claim 11 , wherein the No. 1 shaft and the No. 2 shaft are located within an accessory gear box. 
     
     
       20. The method of  claim 11 , wherein the No. 1 shaft comprises a set of helical gears and the No. 2 shaft comprises a set of helical gears, wherein the helical gears of the No. 1 shaft are intermeshed with the helical gears of the No. 2 shaft. 
     
     
       21. A method of operating a turbine when taking the turbine off-line, comprising:
 transmitting power to a No. 1 shaft via a main motor to turn the turbine at an original turning speed, wherein the No. 1 shaft drives a No. 2 shaft; 
 reducing a speed of the turbine; and 
 when the speed of the turbine is reduced to a predetermined RPM, switching power transmission to the turbine from the No. 1 shaft to the No. 2 shaft, wherein the No. 2 shaft is driven by an auxiliary motor, and the No. 2 shaft drives the No. 1 shaft to turn the turbine at a slow turning speed less than the original turning speed, and upon reaching a predetermined time of running the turbine at the original turning speed or upon reaching a predetermined turbine temperature while running the turbine at the original turning speed, switching power transmission from the No. 1 shaft to the No. 2 shaft.